A difficulty that arose in the early days of personal computers was that of communicating instructions to the computer. Among the most successful ideas for solving this problem was that of inviting a user to point to a selection using a mouse-driven pointer. The selection could be words, such as those on a menu. Or it could be an icon on a desktop. In either case, the central idea was that a pointer selected and activated a particular command.
Touch screens made it possible to dispense with the mouse. With a touch screen, one could simply touch the selection directly. However, the fundamental idea was the same. One would touch what one wanted to select. The main difference was that one could now touch it directly.
The idea of touch screens led naturally to that of virtual keyboards. To enter a letter, the user would touch the appropriate key. The principle was thus the same as it always had been. To cause a result, one would select an appropriate symbol on a display.
This procedure works best when the screen is large enough so that the key can be made commensurate in size with the finger. When the screen becomes smaller, the keys become so small that a human finger can no longer reliably touch the correct key.
An obvious solution would be to use a finger prosthesis, such as a sharp instrument. However, this is inconvenient. Another known solution is that of simply dictating one's selection. However, voice recognition is sometimes unreliable and unsuitable for noisy environments. It is also unsuitable for quiet environments in which many people are present.